SAML (Security Assertion Markup Language) (Ver.2) exists as a standard rule for connecting a plurality of authentication systems. Use of SAML permits achievement of Single Sign-On by which a plurality of Web systems or the like can be used on one single authentication. To use a plurality of Web systems requiring authentication, a user heretofore had to enter authentication information in each Web system. This took time and it was also troublesome to manage authentication data (IDs, passwords, etc.). If Web systems are conformable to SAML, a Web system as a source of movement can communicate with a Web system as a destination of movement by SAML protocol to hand over authentication data automatically when the user moves to the destination Web system.
In SAML, it is necessary to present information as to what authentication system authenticates a user (i.e. authentication destination system information) to authentication servers. In SAML 2.0, authentication destination system information is stored in a user terminal in the form of a cookie which can be received by all authentication servers. Specifically, as shown in FIG. 1, one cookie “Server1” indicating Authentication Server 1 is set in a Web browser of a user terminal by a common cookie setting service. To inform both Authentication Server 1 and Authentication Server 2 of this cookie, Authentication Servers 1 and 2 are heretofore defined in one domain (e.g. common domain common.com) and host names different in authentication servers are set in DNS (Domain Name Server) in the common domain.
In view of setting and action of DNS, it is however practically difficult to let a plurality of authentication servers different in management source (e.g. server1.a.com and server2.other.com in FIG. 1) take part in a common domain (e.g. server1.common.com and server2.common.com).